An organic compound contains $C = 40\%$,$H = 13.33\%$,and $N = 46.67\%$. Its empirical formula is:

$A$ certain compound has the molecular formula $X_4O_6$. If $10 \ g$ of $X_4O_6$ has $5.72 \ g$ of $X$,the atomic mass of $X$ is ............ $amu$.

How much copper can be obtained from $100 \, g$ of copper sulphate $(CuSO_{4})$?

In which of the following pairs of compounds is the ratio of $C$,$H$,and $O$ the same?

In which of the following pairs is the percentage of carbon the same?

Chlorophyll,the green pigment in plants responsible for photosynthesis,contains $2.68\%$ of magnesium by mass. Calculate the number of magnesium atoms in $2.00 \ g$ of chlorophyll.